The Nachlass of A.N. Prior
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Department of Information Studies - University of Copenhagen
Department of Communication and Psychology - Aalborg University


By Arthur N. Prior on NA/NA/NA

This text has been transcribed by Lars Bo Gundersen, Aarhus University, Lars Bo Gundersen, [removed]

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 Knowledgeby A.N. Prior Many philosophers in the past have held such opinions as that nobody really knows that anyone
can think, or feel pain except themselves, that nobody really knows that material things go on
existing when they are not observed, that nobody really knows that the world has been in
existence for more than 5 minutes. And for my own part, I think that the philosophers who have held these opinions have been right. – I subscribe to all of these so-called sceptical views myself. I am conscious, however, that such scepticism is at present a little démodé, and is supposed
somehow to have been finally answered. I am not sure, however, what this final answer is supposed to be, but I would like to consider one or two candidates. It may be said, in the first place, that nobody really believes this, i.e. nobody really believes that nobody really knows that the world has existed longer than 5 minutes, etc. But this will not do, for I believe it. I am tempted to say that I know that I believe it; and if I did say this,
such a claim to knowledge would in no way conflict with the scepticism that I have expressed about other matters. I have not said, nor do I believe, that nobody knows anything at all – though
even this, I think, could be maintained without inconsistency. But I shall not say that I know that I believe that nobody knows, etc.; I'll just say that I'm far from convinced – and I really am far
from convinced – that I do not believe that nobody knows, etc.; and I would have to be
convinced that I do not believe this before I could be convinced that nobody believes it.
The claim could, of course, be abated a bit, and the argument be just that most people do
not believe that nobody knows that the world has existed longer than 5 minutes, etc. Most people in fact believe that they themselves know all of these things that those philosophers say that nobody knows. But when brought down to this, the argument seems very weak. It is surely possible that most people should be wrong. If you took a census you would probably find that most people believe that the number 13 is unlucky, and goodness knows what other absurdities. Truth is in many matters so hard to come by that it would be surprising if most people were not wrong about a great many things, and why should they not be about this thing? It is important at this point to remember what we are talking about. There are matters,
including some which are very close to the ones we are considering now, about which it is impossible that large numbers of people should be mistaken, and some about which it is logically impossible that even two people should be mistaken. In particular, if I say that large numbers of
people, or even two people, are mistaken in thinking that there are other thinking beings beside themselves, I shall have contradicted myself, for you cannot have mistaken thoughts without 
Edited by Lars Bo Gundersen. The MS is handwritten and kept in the Prior Collection at Bodleian Library, Oxford, Box 6. It is undated.
having thoughts. It is in fact my own firm belief that there are other thinking beings, that there are beings who feel pain, that there are objects which go on existing unobserved, and that the world has lasted for very much longer than 5 minutes; and if I am mistaken about the first of these things, that is if I am mistaken in thinking that there are other thinking beings, then I am the only person who is making this mistake; in fact if I am mistaken about this then nobody else
is mistaken about anything (or, of course, right about anything either). Similarly, people could not have been mistaken for centuries about how long the world has lasted, or about anything else,
if in fact the world has only lasted for 5 minutes.But all this is not in question. The question is not whether these things are true, but
whether they are known, and the point on which I think the majority of people are probably
mistaken is not in their belief that other people beside themselves think, and feel pain and so on, but in their belief that they know these things. And I do not see why the majority of people
should not be mistaken about this, as they are almost certainly mistaken about a great number of other things. However, the anti-sceptic's gun has another barrel. It may be said that scepticism of the sort we are considering runs counter to the ordinary and accepted use of the word 'know' – a point on which, as even Hume admitted, 'the vulgar' really do have some authority. It would seem odd, on the face of it, that the word 'know' should contain as part of its very meaning anything at all about what we know in fact, but it would be unwise to dismiss the previous
objection with any general observation of this sort, for we do often gather how a word is being used from what people commonly say with it, and even more from how they defend what they say. So let us look at one or two cases. # I am not sure how 'ordinary' my first case is, but I shall begin with a confession – I very nearly started off this paper by saying 'We all know that many philosophers have held, etc. etc.', but then dropped this manner of introduction as being inconsistent with what I was going to say later. If we all know that philosophers have had such and such opinions, then we all know that there are or have been other thinking beings beside ourselves, so that at least the first of these philosophical opinions is wrong. And I've no doubt that if anybody thought it worth while to flip through things I have written, they would find me
saying things of the sort which here I have been especially careful not to say. 'We all know that' is a phrase of which somewhat rhetorical people like myself are only too fond. The worst example of course is the politician who tells us that the whole world knows that XY, XY being generally some monsterous lie. This seems enough to rule this example out – we are not here concerned with rhetoric, but with serious claims to knowledge. At the same time, it is possible to put a somewhat less disreputable construction on what I almost did, as we shall see after considering another case. 'Could Philip Partington have committed the murder? We know, at any rate that he was
on the scene of the crime shortly afterwards.' Here it seems clear that all that is intended is that this, i.e. that Partington was on the scene of the crime, is not now in dispute – there has been sufficient investigation of it for us to be able to take it for granted without further inquiry, and
use it in our later reasonings. And this use of 'know', I suspect, is very common indeed. The 'We all know that' which we introduce into learned discourses often has just this force – it marks off the starting-point, which we expect our hearers to share, from subsequent theses about which we expect to have to put up a case. If someone said 'But do we know this?' we would be a little
shocked – we would feel, not that what we have said was really doubtful, but that we have misjudged our audience. 'Do I really have to go over all that?' we might ask with impatience. – 'It wasn't what I was planning to talk about at all'. We might, of course, 'go over all that' nevertheless, and for our own satisfaction as well as the questioner's. And we might take this very fact as showing that we did not really 'know' the thing at all. But we might not. We all know this story of G.H. Hardy putting up a formula and saying 'This is obvious', and then asking himself 'Well, is it obvious?', filling the blackboard with
a proof of it, and then saying 'Yes, it is obvious'. The story is generally told to show that the mathematician's notion of 'obvious' is a little mad; but it is at least a natural development of a tendency which is quite common in the use of such words. To claim that something is 'known' or 'obvious' is often just to claim that we are entitled to rest on it, to use it, to take it for granted, and going over the proof or evidence again may be taken as showing that we were so entitled all the
time. There does seem here to be an ordinary use of 'know' in which it is entirely correct to say that we know that other people, unobserved material objects and so on, exist; and no doubt other and better examples of such a use could easily be found. I would only insist that such a use is neither as common nor as secure as it is sometimes alleged – not so secure, because it is not difficult to talk people out of such claims by the usual sort of needling ('Did you really see Partington there with your own eyes?' Are you sure you weren't dreaming? That you haven't been hypnotised? And so on and so on.) After all, sceptical philosophers have had a vogue, have
successfully worried people, and often where they haven't converted them have driven them into claiming that we can 'know' the existence of other people, etc. in a rather stronger sense that this common one. But I have no real interest in denying that there is this weaker ordinary sense of 'know', or even in denying that when the sceptical philosopher says what he does say he is using 'know' in a strained, technical, and as Paul Edwards would say a 'high-redefined' sense. For we need not quarrel over words, and if the self-styled non-sceptic admits that we do not 'know' that other
people exist, and so on, in the sceptical philosopher's sense of 'know', however strained and 'high-redefined' this may be, then he is admitting all the sceptical philosopher wants to maintain. And if he says that no ordinary person would be worried by the sceptic if he realised what the sceptic meant by 'know', I can only say that I very much doubt this, but don't think it important – épater les bourgeois is not, after all, a philosophical end in itself.
But the anti-sceptic may go further than this, and now we come to an argument which really has worried me. He may contend not merely that the philosopher's sense of 'know' is a very peculiar one, but that there is no philosopher's sense of 'know' – that if you push the sceptic
into explaining what this special thing is that he means by 'know', whatever anyone else means
by it, he cannot give any answer that will bear examination. The essential thing about the philosopher's sense of 'know' is of course some kind of claim to infallibility – he who really knows anything cannot possibly be wrong, cannot be corrected, cannot turn out to be mistaken. But when we examine the force of this 'cannot' we either end up with something too weak for what the sceptic wants to do with it, or with something too strong. The form of speech 'If p then necessarily q' admits of only two interpretations that are at all obvious. In the first sense you bracket the 'necessarily' with the 'then', and the form as a whole simply means that q necessarily follows from p. And of course if anything is known it follows that it is true, and if it is not true it follows that it is not known. But this much can be said of true belief – if we believe truly that p, however much this may be a matter of sheer good luck, it follows that it is the case that p, and if it is not the case that p then nobody can believe with truth that p. But whatever the sceptic means by 'knowledge' it isn't merely true belief – in denying that anybody knows that there are other people or unobserved objects, the sceptic is not denying that
the beliefs that there are other people and unobserved material objects are true; in fact he usually shares these beliefs himself. (Scepticism is one thing; solipsism and Berkeleyan immaterialism are quite other things). On the other hand, the form of speech 'If p then necessarily q' may also be read with the 'necessarily' bracketed with the 'q', so that the whole form means that if p is true then q is in itself a necessary truth. Applied to the particular case 'What is known cannot be false', this would mean that only necessary truths are known, a position which very few sceptics have maintained. Is there any third alternative? What the sceptic is feeling after is clearly some kind of unbreakable attachment of knowledge to what is known, which is not present where we merely
have true belief, however solidly grounded. Can this notion of unbreakable attachment be given any clear and unfigurative sense? I am not at all sure that it can, in which case scepticism must be admitted to fail by incoherence, but I shall make a small effort at a patch-up, and then end. Let us begin by asking what your sceptic generally does allow to be 'known' in his sense of the word. Normally it boils down to two things – the truths of logic and the immediate deliverances of the senses – 'sense-data', if I may dare to use this term. But it is not at all clear to me why the truths of logic are included, since this is a field in which we obviously do make mistakes very frequently. No doubt we are pretty unshakeable as far as the very simplest logical truths are concerned, but I cannot believe that so sharp a line as that between genuine knowledge and confident ignorance can be drawn on the basis of anything so messy and subjective as a distinction between the simple and the complicated. And remember even so simple a logical principle as the law of excluded middle has been alleged by very reputable thinkers to be mistaken. So on reflection this sceptic, for one, prefers to leave the laws of logic out of it. What is left? Stripping the thing clear of dubious accusations, what is left is the way things seem to be.
We cannot be mistaken, the argument now runs, about how things seem to us to be, and we do
not know anything else in the way that we know how things seem to us to be. But what – we must ask it again – is the force of the 'cannot' in this 'cannot be mistaken'? I would suggest this: If anything seems to us to seem to us to be a certain way, then it really does seem to us to be that way – this is part of the special logic of 'seeming'. And what makes me rather confident of the principle that I have just enunciated is that Wittgenstein at one point in Philosophical
Investigations says, or anyway implies, that it is meaningless. By and large, it is a safe principle
of philosophical methodology, that if Wittgenstein says that a thing is meaningless, it is a necessary truth. This is the unbreakable bond that exists between knowledge and its object in the only case where the sceptic, when thoroughly pressed, admits that 'knowledge' in his special sense of the word exists. X may seem to us to be Y for a variety of reasons – sometimes because it is Y, but sometimes for other reasons – but X can only seem to us to seem to be Y because it does seem to be Y. That X seems to me to be Y may not in itself be a logical truth (perhaps cannot be one), and 'X seems to me to seem to me to be Y' does not entail 'X seems to me to be Y' in virtue of any truth-table tautology (in the way that 'A believes truly that p' i.e. 'A believes that p, and p' entails as its own conjunct the plain 'p', but by the special logic of 'seeming' – that's the special connexion between knowledge and its object that is present here and nowhere else. There is one other hurdle here, however, and I confess I do not know how to jump it. What is this 'seeming to be so'? Does 'X seems to me to be Y' just mean 'I think that X is Y', so
that the above principle can be re-stated as 'If I think that I think that p, then I do think that p'? If it can be so stated, then there are strong reasons – too complicated to be given here, but I have given them elsewhere – for regarding it as false. But what else does it mean? This is another of the things that I must confess I do not know. •  University of Copenhagen •  Aalborg University •